§79. Irregular Nouns of the Third Declension

In many nouns the stem is irregularly modified in the nominative or other cases. Some peculiar forms are thus declined:—

a. Two vowel-stems in ū-, grū- and sū-, which follow the third declension, add s in the nominative, and are inflected like mute stems: grūs has also a nominative gruis; sūs has both suibus and sū˘bus in the dative and ablative plural, grūs has only gruibus.

b. In the stem bov- (bou-) the diphthong ou becomes ō in the nominative (bōs, bŏvis).

In nāv- (nau-) an i is added ( nāvis, -is), and it is declined like turris (§ 67).

In Iŏv- (= Ζεύς) the diphthong ( ou) becomes ū in Iū-piter (for -păter), genitive Iŏvis, etc.; but the form Iuppiter is preferred.

c. In iter, itineris (N.), iecur, iecinoris ( iecoris) (N.), supellēx, supellēctilis (F.), the nominative has been formed from a shorter stem; in senex, senis, from a longer; so that these words show a combination of forms from two distinct stems.

d. In nix, nivis the nominative retains a g from the original stem, the g uniting with s, the nominative ending, to form x. In the other cases the stem assumes the form niv- and it adds i in the genitive plural.

e. Vās (N.), vāsis, keeps s throughout; plural vāsa, vāsōrum. A dative plural vāsibus also occurs. There is a rare singular vāsum.